On 2004-03-02, at 18:26:33 +0000, Nick Ing-Simmons wrote:
Marcus Holland-Moritz <[EMAIL PROTECTED]> writes:
Core perl uses magic macro to set errno which IIRC does back convert to native error code on VMS and Win32 ?
Yes, but there's no way (that I could see) to set the PV slot in $! to a user-defined string. You can assign any number to $!, but that's almost useless:
[EMAIL PROTECTED] ~ $ perl -e '$!=4711;print"$!\n"' Unknown error 4711
Furthermore, the whole concept of Errno and %! wouldn't work.
So you have to set errno to one of the known values, and have a resonable idea what message you get.
Exactly. :)
So: EINVAL
EBADF
EAGAIN
EWOULDBLOCK
yeild fairly generic messages. Linux has a lot of exotic ones but they ain't portable.
You could probably check which keys are in %! at Makefile.PL time, and use more specific messages where available. But I don't think that would help very much.
So what we are supposed to do if we want to keep the idimatic perl working?
Consider:
open my $fh, "</tmp/bar" or die "$!";
now if I want to implement a perlio layer, I want this to work just the same:
open my $fh, "<:mylayer" or die "$!";
How do I set $! then? perlio doesn't provide a framework to set $!, just return codes.
At the moment the only option is to croak. But that totally breaks idiomatic perl, making the API kludgy as you need to eval {} every statement if you want to trap the error yourself.
Or is introducing a new $! variable like DBI::errstr a better way? It works for DBI since it provides a new API. Whereas with perlio the API doesn't change from the core API, but error handling is totally different.
can't we attach a different magic to $!, which will override ERRNO magic, if the former exists?
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